Recently, those in the art of manufacturing movable barriers, such as flexible roll doors, have provided separable connections between the barrier and the means for guiding the barrier within the confines of the opening. The separable connection is provided to minimize damage in the event of an impact on the barrier, such as by a service vehicle.
The first and most comprehensive development in this area to date is disclosed in U.S. Pat. No. 5,025,847, issued to Mueller, and assigned to the Assignee of the present invention. Mueller discloses a roll door having a two-part guide follower. This guide follower is designed to separate to allow the door and one part of the guide follower to be released from the other part of the guide follower in response to an excessive transverse force.
The separable connections of Mueller and subsequently others operate on the principle that the connections are slidingly separable. Particularly, a first member attached to a guide mechanism in the door jambs extends toward the barrier and a portion thereof is cooperatively fitted into a receptacle-type structure in the barrier. Most frequently, this receptacle is formed in a rigid leading edge of the barrier, commonly referred to as a bottom bar of the barrier. In the event of an impact, in excess of a predetermined magnitude, the guide follower separates and the barrier is allowed to move transversely of the opening without damage to the door or to the guide followers. Such systems have found widespread use and have been found to significantly reduce the damage to overhead doors caused by unintended impacts, as, for example, with a moving forklift.
However, it has been discovered that, during some impacts, the bottom bar of the movable barrier becomes rotated. The bottom bar may also be forced into a translational motion in a direction which, while generally transverse to the plane of the barrier, is not 90.degree. with respect to the plane of the barrier. On these occasions, upper and lower surfaces within the receptacle can jamb or bind on upper and lower surfaces of the first member. This can cause a substantial increase in the amount of force required for separation of the two components. In extreme cases, the resistance will so far exceed the desired predetermined separation force as to cause damage to the movable barrier and possibly to the guide means and associated apparatus.
While operating on the same broad principles as disclosed in Mueller, the present invention is directed to solving the above problems and to provide further improvements over the basic structures known in the prior art.